Search for: All records

Transmission electron microscopy (TEM) continues to transform polymer science by revealing key aspects of chain packing, phase separation and nanoscale structure. The development of instrumentation and data analyses tools is driving the field forward and enabling new experiments. Here, we use automated high-resolution TEM (HRTEM) and image processing to identify the structure of a conjugated polymer used in organic electronics. Analysis of more than 600 HRTEM images reveals lattice parameters and orientation correlations between crystals, including the preferred alignment of neighboring crystals along the same crystallographic direction that is likely the result of liquid crystalline order. 

Soft and conducting organic materials are ideal candidates for stretchable bioelectronics and wearable devices. Despite recent advances, our understanding of conducting polymer nanostructures and how they arise remains incomplete, given the limited high-resolution studies and molecular-level descriptions of these systems. Here, we employ cryogenic transmission electron microscopy (cryo-EM) to investigate the evolution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) morphology in solution and the resulting solid state structure in the presence of ionic and molecular additives. Our results reveal the formation of heterostructural elongated fibers consisting of PEDOT:PSS micelles in solution. Cryo-EM further reveals that additives increase the number of fibrils, in addition to inducing the formation of crystalline domains. We observe that fibril and crystalline phases in solutions act as a template for the growth of these nanostructures in the solid state. Furthermore, exploiting cryo-EM reveals the role of solid-liquid interactions in PEDOT:PSS through the imaging of PEDOT:PSS nanostructures after the hydration of thin films. Hydration leads to the swelling of heterostructural fibers while reducing the crystalline domain size. Such behavior explains the mechanical robustness of PEDOT:PSS thin films processed with various additives as well as the high electrical conductivity of PEDOT:PSS in applications such as organic electorchemical transistors. 

Gratev2 enables near-real time HRTEM analysis: a graph-based pipeline extracts d-spacing, orientation, and shape metrics; Bayesian optimization auto-tunes parameters; a Wasserstein-distance signals when data collection is sufficient.